1. Field of the Invention
The present invention relates to control devices for rotating electric machines.
2. Description of the Related Art
There has been proposed a control device for rotating electric machines capable of reducing noise or radiated noise in a rotating electric machine generated during the rotation of the rotating electric machine. Such conventional control devices suppress electromagnetic force induced in the radial direction of the rotating electric machine in order to reduce radiated noise.
Patent document 1 discloses such a conventional control device for rotating electric machines. The control device disclosed in patent document 1 is applied to an inner rotor type rotating electric machine, and reduces m-th order electromagnetic force component because it is effective to reduce a 6M-th electromagnetic force component applied in a radial direction to a stator.
In a concrete example, the control device for rotating electric machines disclosed in patent document 1 calculates a fundamental current on the basis of a torque instruction value and a motor rotation speed, and superimposes a harmonic current over the fundamental current. In this case, the harmonic current has an angular velocity of 6M−1 or 6M+1 times a rotation angular velocity of the fundamental current. This control makes it possible to reduce the 6M-th electromagnetic force component applied to the stator of the rotating electric machine.
By the way, such noise is generated by the electromagnetic force applied to a rotor in a radial direction when the rotating electric machine is an outer rotor type. For this reason, it is desired to reduce the electromagnetic force applied to the rotor in such outer rotor type rotating electric machines.
However, there is a possible change such that the load of the rotating electric machine varies even if the rotation angular velocity of the fundamental current is constant. When the load of the motor varies, there is a possible risk that it is difficult to correctly reduce electromagnetic force which causes noise if the harmonic current having the same condition before the change of the load of the rotating electric machine is superimposed over the fundamental current.